Similar to the safety regulations and requirements for most motor vehicles travelling along the highways and byways of the United States, inflatable airbag systems are required in most aircraft which traverse U.S. airways. Also, similar to the National Highway Safety Administration which issues and administers Federal Motor Vehicle Safety Standards (“FMVSS”) regarding the manufacture of motor vehicles and equipment therein, the Federal Aviation Administration (“FAA”) establishes standards for the regulation of aircraft and equipment utilized therein, including Federal Aviation Requirements (“FAR”). Other airworthiness authorities operate around the world, and a great majority of them adhere to the safety standards set by the FAA.
Among these common requirements, are constraints of flammability of airbag materials, regulated for automobiles via FMVSS 302, and for aircraft via FAR 25.853. More in particular FMVSS 302 establishes a horizontal burn test requirement for fabrics used in the airbags installed in automobiles for use in the United States.
The FAA, however, has established a more stringent vertical burn requirement for fabrics utilized in the material of construction of inflatable airbags for use in aircraft by way of FAR 25.853. Currently, however, no fabric is known or utilized in the aircraft industry which meets the vertical burn requirement of FAR 25.853, and therefore, the FAA has been forced to provide a waiver of the vertical flammability requirement, instead acceding to the horizontal burn test requirements of the less stringent FMVSS 302 horizontal.
According to the FAA, “[w]hile inflatable airbags are now standard in the automotive industry, the use of inflatable-airbag systems in commercial aviation is novel and unusual.” (Special Conditions: Cessna Airplane Company Model 680A Airplane, SideFacing Seats Equipped With Airbag Systems, 14 CFR Part 25 [Docket No. FAA-2015-2271; Special Conditions No. 25-602-SC] Oct. 6, 2015.) Furthermore, the FAA recognizes that the state-of-the art for airbag fabrics do not adequately meet the performance and flammability requirements required to keep passengers safe in aviation applications, stating, “the specialized function of the inflatable-airbag system means that highly specialized materials are required. The standard normally applied to fabrics is a 12-second vertical ignition test. However, materials that meet this standard do not perform adequately as inflatable restraints; and materials used in the construction of inflatable-airbag systems do not perform well in this test.” (Id.)
Table 1, below, provides a comparison of the flammability requirements between FMVSS 302 horizontal, FAR 25.853 horizontal, and FAR 25.853 vertical.
TABLE 1FMVSS 302FAA 25.853FAA 25.853HorizontalHorizontalVerticalDistance from 0.748 in0.75 in0.75 inflameFlame exposure15 seconds15 seconds12 secondsBurn requirement60 secondsN/A15 seconds(stop)Burn requirement2.01 inN/A8 in(length)Burn requirements 4.02 in per min2.5 in per minN/A*(rate)Burn requirements N/AN/A5 seconds(drippings)*Must be self extinguishing
FIG. 1 shows samples of current automotive airbag fabric versus the aviation airbag fabric produced using the method taught by the present invention, when tested to the requirements of FAA 25.853 Vertical Burn Test.
In addition to the flame test requirements under FAR 25.853, materials of construction for inflatable airbags for installation in aircraft must also meet a high pressure permeability resistance. More in particular, fabrics for use in aviation airbags must exhibit a high pressure permeability resistance which is measured as a pressure of not less than about 198 kilopascals (“kPa”) after five seconds from an initial inflation and pressurization to 200 kPa.
Previous attempts in the art directed to providing airbags for use in aviation applications merely present conventional airbags and request a flammability waiver from the FAA. Indeed, a search of the prior art airbags and methods of making airbags yields many that make reference to their use in vehicles “including aircraft,” but provide no disclosure as to what features, if any, make them suitable for use in aircraft.
Indeed, merely utilizing “flame resistant” fabric is not sufficient to meet the stringent FAA vertical burn requirements of FAR 25.853. FIG. 1 shows the difference between flame resistant fabric as is used in current airbags, as well as the aviation airbag fabric disclosed herein, when tested to the vertical burn requirements of FAR 25.853.
Attempts in the art to impart improved fire resistance have been at the expense of air permeability performance. As stated by the FAA, and noted above, materials that meet the fire resistance standard do not perform adequately as inflatable restraints; and materials traditionally used in the construction of inflatable-airbag systems (such as in land vehicles) do not perform well in the FAA vertical burn test.
At the present time the Federal Aviation Administration (“FAA”) of the United States of America has issued a number of Federal Aviation Requirements (“FAR”) directed to various aspects of aircraft construction and operation. Among these requirements is Federal Aviation Administration FAR 25.853 which includes, among other things, vertical flammability requirements for materials used in many aircraft operated in the United States. More in particular, in accordance with FAR 25.853 a material for use in aircraft in the United States must meet vertical flammability requirements which include, a flame time which is not to exceed fifteen seconds, a burn length, which is not to exceed eight inches, and a drip flame which is not to exceed five seconds.
Once again, as stated above, at the present time there are no fabrics known which meet the stringent requirements of FAR 25.853 for vertical flammability which may utilized for construction of aviation airbags in aircraft operated in the United States. As such, the FAA has indefinitely waived this requirement provided that any fabric utilized for aviation airbags is sufficiently flame resistant to pass the less stringent requirements of a horizontal flame test in accordance with the Federal Motor Vehicle Safety Standard 302.
The table presented in FIG. 1 is illustrative of the results obtained for a nylon fabric which is coated with 30 grams per square meter (“gsm”) of liquid silicone rubber, as is typical for use in airbag fabrics utilized in automobiles in the United States, when the fabric is subjected to vertical flammability testing in accordance with FAR 25.853. As is readily apparent from the results presented in FIG. 1, a nylon fabric coated with liquid silicone rubber fails to meet the requirements for vertical flammability resistance under 25.853. In accordance with at least one embodiment of the present invention, a flame resistant fabric for aviation airbags comprises the uncoated polyester fiber.
In view of the foregoing, it is understood and appreciated by those of skill in the art that it will be beneficial to provide a flame resistant fabric for use in the construction of various components for aircraft, including, but not limited to, aviation airbags. A further benefit may be realized by providing a flame resistant fabric which meets the vertical flammability requirements in accordance with FAR 25.853. Yet another benefit may be realized by providing such a flame resistant fabric which also comprises high pressure permeability resistant which is in compliance with FAA requirements.
It would be further appreciated from the foregoing that considerable benefits will be realized for the safety of passengers and crew in aircraft flying throughout the world to provide a flame resistant fabric for the construction of aviation airbags which meets the stringent vertical flammability requirements of FAR 25.853 as well as meeting the FAA's high pressure permeability resistance requirements, such as the present inventive flame resistant fabric discussed in greater detail hereinafter.
While certain aspects of conventional technologies and methods in the relevant art have been discussed to facilitate disclosure of the invention, Applicant in no way disclaims these technical aspects or methods, and it is contemplated that the claimed invention may encompass one or more of the conventional technical aspects or methods discussed herein.
In this specification, where a document, act, or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act, or item of knowledge or any combination thereof was, at the priority date, publicly available, known to the public, part of common general knowledge, or otherwise constitutes prior art under the applicable statutory provisions; or is known to be relevant to an attempt to solve any problem with which this specification is concerned.